Secondhand cars are displayed at the Guangjun Used Auto Market in the southern Chinese city of Guangzhou.

GUANGZHOU, China — As car enthusiasts converge on the annual Guangzhou auto show, few have anything except a shiny new set of wheels in mind. But explosive growth that transformed China into the world’s largest auto market is also giving life to a new industry here: used cars.

Chinese started buying new cars in huge numbers about four years ago, about the average length of time analysts say drivers will stick with a vehicle before trading it in for a fresh model.

The secondhand market is already taking off, with sales growth last year outpacing that for new vehicles. By volume it is still dwarfed by new cars, which outsold used vehicles three to one. In countries such as the U.S., that ratio is reversed, highlighting the secondhand market’s vast potential to make car ownership affordable for millions more Chinese.

The challenge in China is to develop a modern market for secondhand autos. The business is dominated by thousands of small trading companies that operate out of big trading halls or open air markets on city outskirts. Vehicles are sold tax free and ownership can be transferred in a day but quality and fair pricing can be uncertain. By some estimates, four in five used car transactions take place at these markets.

For foreign automakers, “the used car business in China is very different to anything that you would recognize in the Western world,” said Marin Burela, president of Changan Ford, the U.S. company’s China joint venture.

Global automakers have been slow to add used car sales at dealerships but are now racing to expand into the business, which will diversify their revenue and help build brand loyalty.

Liu Yu-chen, a 28-year-old snack food entrepreneur, plans to buy his first secondhand car after owning a series of new vehicles, the latest a Toyota Prado SUV bought in August.

“After conducting a good inspection, you just need to figure out whether the car appears to have been in any accidents,” said Liu as he browsed vehicles at Guangzhou’s Guangjun Used Car Market, which houses dozens of small auto trading companies.

He is budgeting up to $164,000 for a used Land Rover and doesn’t consider the price tag high. Luxury autos tend to be more expensive in China because of taxes and foreign automakers pushing the limits of what they can charge.

“What I want to buy is a well maintained car, no damage. Scratches don’t matter. If there’s no big problem with the bumpers, no weird sound from the engine, then I’ll consider it,” said Liu, who flew from his home in the central city of Xian to car shop in the southern economic boomtown because he thought they would be cheaper.

Last year in China, used car sales rose 11 percent to 4.8 million vehicles, while new car sales rose 7 percent to 15.5 million. Ford’s Burela, speaking at the Guangzhou auto show which runs through today, said the industry expects used car sales of 6 million this year, about 10 million in 2016 and 20 million by 2020, putting it on par with new vehicle sales.

About half of Ford’s 500 dealerships have been approved to sell “certified” used cars that come with warranties. The company has also opened six showrooms this year selling only secondhand vehicles.

Dealers in China will need to focus on used auto sales to raise their profit margins as new car sales start to plateau. In the U.S., about 55 percent of a dealer’s revenue comes from new vehicle sales while 25 percent to 30 percent comes from secondhand sales, and the rest from parts and servicing.

But in China, new car sales have accounted for 90 percent of revenue, said Ivo Naumann, Shanghai-based managing director of advisory firm AlixPartners.

Chinese brands, unpopular because of quality concerns, will likely fall further behind the dominant foreign brands including General Motors, Volkswagen, Toyota and Nissan as the secondhand market develops, Naumann said.

“Some people who probably historically would have bought a new car because they were first time buyers, they’ll say: Well I only have $8,000, I could buy a Chinese brand, low quality, or I could buy this second hand car from Volkswagen. And then that can have an impact on the overall market,” Naumann said. Because China’s auto industry is still new, there are bottlenecks holding back growth of the secondhand trade. For one, there’s no system of easily transferrable temporary plates for dealers, constraining the number of cars they can have in stock.

Another problem is lack of accurate and consistent information about prices. Beijing-based Bitauto Holdings, which runs a car pricing and listing website, is teaming up with U.S. company Kelley Blue Book to launch a China price guide next year using data on 1 million transactions from their other partner, the China Automobile Dealers Association.

Some dealers have adopted the latest technology. Dongfeng Nissan, the Japanese company’s China joint venture, has its own system to assess trade-in values. Staff use iPads to carry out a step-by-step check. They can photograph scratches or other damage and upload it.

“The system will automatically prompt an overall score on this car and a recommended resale price to staff,” said deputy general manager Yasuhiro Konta.

Currently, most owners who want to sell a car will typically take it to between three and five traders to get an idea of price, usually an estimate by a senior employee based on their own judgment, said Bitauto’s chief financial officer Andy Zhang.

“The whole experience is fairly insecure,” Zhang said. “It’s very important to have those benchmark prices out there.”